1. Field
This application relates to a method of fabricating a semiconductor device capable of increasing a breakdown voltage without an additional epitaxial layer or buried layer with respect to a high-voltage horizontal MOSFET.
2. Description of Related Art
In a conventional N-type LDMOS (Lateral Double diffused MOS), a body region that includes a source region is connected to a ground, and a breakdown voltage from a high concentration N-type (N+) source region to the body region is highly limited. Particularly, the breakdown voltage is typically much lower than about 20 V.
Various methods have been suggested to increase the low breakdown voltage of an LDMOS device. By way of example, there is a method of forming a deep well extending from a drain region to a P-type body region surrounding a source region so that the deep well surrounds the P-type body region, or a method of forming a low concentration N-type extension region surrounding a high concentration N-type source region. Although it has been possible to increase a breakdown voltage by a certain amount using these methods, it has not been possible to obtain a breakdown voltage of 100 V or more.
Further, in a method of forming a high concentration N+ buried layer between the substrate and a deep well region while forming a thick epitaxial layer on a substrate, a method of fully isolating the P-type body region and the substrate was also suggested. Nevertheless, there were problems in that not only does a technical configuration to form a buried layer and a thick epitaxial layer require a high unit price, but also many applications exist that do not require this fully isolating technique.